Abstract / Summary
Abstract Objective Computed tomography (CT) quantifies emphysema extent but not the accompanying perfusion loss. This study evaluated whether perfusion defect extent, the percent perfusion defect (%PPD) on short-time deep-inspiratory breath-hold (STDIBH) perfusion single-photon emission computed tomography/CT (SPECT/CT), is associated with major adverse events (MAE) in emphysema, and whether CT-quantified emphysema extent carries comparable information. Methods Of 91 patients with emphysema who underwent STDIBH perfusion SPECT/CT, 74 were analyzed retrospectively. Perfusion defect volume as a percentage of CT lung volume defined %PPD, and emphysema extent was the percentage of low-attenuation area (%LAA) on the same CT. MAE comprised all-cause death, hospitalization for respiratory failure or acute exacerbation of chronic obstructive pulmonary disease, and new home oxygen therapy. The primary analysis was Cox regression adjusted for B-type natriuretic peptide and for combined pulmonary fibrosis and emphysema (CPFE), supplemented by clinical adjustment, penalized estimation, restricted cubic splines, and exploratory time-dependent areas under the curve (AUCs). Results Over a median follow-up of 70.9 months, MAE occurred in 54 patients (73.0%). In the primary model, %PPD was associated with MAE (hazard ratio [HR] 1.1641 per 10%, 95% confidence interval [CI] 1.0437–1.2982, P = 0.006), and the estimate was similar after adjustment for age, sex, percent predicted forced expiratory volume in 1 s, and CPFE (HR 1.1651, 95% CI 1.0392–1.3063). Unadjusted %LAA was not significantly associated with MAE (HR 1.0080 per 1%, 95% CI 0.9884–1.0280, P = 0.425). The time-dependent AUC of %PPD exceeded that of %LAA at 36 months (difference 0.183, 95% CI 0.069–0.303) and 60 months (0.189, 0.044–0.338) but not clearly at 12 months (0.050, − 0.069 to 0.164). Risk rose up to a %PPD of about 55% and no further (nonlinearity P < 0.001). The planar Meyer perfusion score discriminated MAE similarly to %PPD (binary AUC 0.813 vs 0.776, P = 0.263). Conclusions In pulmonary emphysema, perfusion defect extent on STDIBH SPECT/CT, not CT-quantified emphysema extent, tracks major adverse events. Because STDIBH SPECT/CT measures the perfusion defect against the same CT that quantifies emphysema, one examination places the vascular and structural components of the disease on a common anatomical denominator.